In this paper, we built a kernel image of a real-time operating system (RTOS) using the host operating system. Ubuntu 18.04 LTS is chosen as the host operating system as its performance and support features are better as compared with other operating systems. RTEMS is chosen as real-time operating system because, it is open-sourced, and its performance is comparable with the proprietary real-time operating systems. Building a kernel image of RTEMS can be achieved by the following steps. By source building, kernel image of RTEMS is generated which is compatible with the generic architectures. As the applications depend on the hardware used, we need the kernel image which is compatible with the desired hardware. It is achieved through cross-compilation. The executable files of RTEMS kernel image are generated by make the file process. These files can be ported to the desired hardware and applications can be achieved. © Springer Nature Singapore Pte Ltd 2021.